GB/T 25744-2010 in English

《GB/T 25744-2010钢件渗碳淬火回火金相检验》由TC75（全国热处理标准化技术委员会）归口，主管部门为国家标准化管理委员会。

1 Scope

This standard specifies the metallographic structure examination for carburizing quenching and tempering of steel parts, metallographic structure grades, and determination methods for the effective depth of carburizing quenched and hardened cases.

This standard is applicable to the workpiece with the effective depth of carburizing quenched and hardened cases greater than 0.3 mm.

2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this standard. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition applies.

GB/T 7232 Terminology of metal heat treatment
GB/T 9450 Steels - Determination and verification of the depth of carburized and hardened cases (GB/T 9450-2005, ISO 2639: 2002, MOD)
GB/T 13298 Inspection methods of microstructure for metals

3 Terms and definitions

For the purposes of this standard, the terms and definitions given in GB/T 7232, as well as the following apply.

3.1

core structure

the structure with a distance of 3 times the effective depth of the carburizing quenched and hardened cases from the surface

4 Specimen

4.1 The specimen shall be taken from the representative service area of the workpiece, or the furnace specimen corresponding size shall be taken. The surface roughness of the furnace specimen shall be the same as that of the workpiece.

Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Specimen
5 Inspection items and methods
6 Evaluation of metallographic structure grades
7 Instruments for inspection
8 Inspection report
Annex A (Informative) General provisions for metallographic examination for carburizing quenching and tempering of steel gears
Annex B (Normative) Schematic diagrams for martensite grades
Annex C (Normative) Schematic diagrams for retained austenite grades (500x)
Annex D (Informative) Schematic diagrams for retained austenite grades (1,000×)
Annex E (Normative) Schematic diagrams for carbide grades
Annex F (Informative) Internal oxidation morphology
Annex G (Normative) Schematic diagrams for core structure grades